Cs MonSys Hydraulic Hardware

• 9.5 km of straight and bent calibration tubes sequence for 3 independent subsystems: EBA, EBC, LB

• > 2 km of supply tubes & pipes

• ~2500 interconnections: glued mostly

• Pressure sensors (PS): ~60+20

• 3 + 3 + 3 sources “garages”

• Liquid storage units: 200+100+100 liters

• Pumping and control equipments

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The system was assembled in the pit in 2004-06 and operated since March 06’. The real sources are installed in Dec 07 and all the operations continued till March 2013 at the rate close to one “full scan” every 2-3 weeks: LB – one round over 64 modules and EBA&EBC – two rounds: “forward” & “backward”. In average the scan takes 6-8 hours.

Detected and potential leaks at the detector

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• Used liquid is a water solution mixture of a number of chemicals (up to 15%) – the leak traces are clear visible and the residue creates “3D” white spots. Being alkaline the liquid might create problems to other (first of all electronic) equipment

• The liquid was not drained last 4-5 years because of a few reasons. Static pressure at the detector is 1-2 bars. Applied variable pressure difference is within the limits ±1.5 bars thus local pressure any point inside the piping might reach ~3 bars for a short period while the source capsule travel through 4-8 modules (~10 minutes)

• Glue connections of the bent and straight tubes: two leak cases May 2007 (LB) – repaired using gel glue and ~2012 (LB) – currently detected problem

• PS – no leaks found yet

• Garages: looked as the problems appeared in 2012 in all the garages but were not recognized at the moment so, the leaks in all three partitions took places. The upper limit on all the losses of the liquid is up to ~10 liters in total (~1kG of the residue)

• Supply pipes: it looks like flexible pipes (~1.5 km) are the source of the liquid color change after more than 5 years. In principle, the pipes might leak if the liquid weakens the pipes chemically or there are the problems with the fitting. No leaks comes from the pipes yet and no indication on the piping damage found but the point has to be looked after.

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Points and places of potential leaks: glued tubes, supply pipes, TEEs (PS) and the garages

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Measurements / Approaches

The first thing to be done is to fix the current problems and take all the possible measures to prevent the leaks in the future. Thoroughgoing measures might be “passive” – desirable changes of the working conditions and modes of operations (including protections and shields of the sensitive equipment) and “active” – change of the design (at least partially), used materials or even the working media.

Repairs and passive measures might be done and taken as soon as possible; the active ones only after preliminary studies and tests done.

If the reason of the leaks from the garages is clear – bad gaskets material, the glue connection cracks is a mystery.

It might come either from the initial mistake at the assembling (technology violation) or from later physical impact (“friendly fire”) – during pit works some people used our bent tubes as cable / pipes supports and even as handles…

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Glued tubes interconnection

The first case (LB, 2007, TLB#22, inaccessible point) problem was solved using gel glue (SFR commercially available liquid). Today we can use the same technique.

The steps supposed to be the following:

The inner tubes volume of the section is filled with a mixture of clean water and SFR glue (~3-5%); applied pressure is around 2-3 bars Some time (1-3 hour) the liquid circulates using pumping and distributing equipment; if access exists, the leak point is supervised The mixture is drained, the inner volume is rinsed with fresh water The success of the operation is confirmed with pressurized (3 bars) air long (a few days) test If the leak persisted (detected by pressure drop) the operation is repeated

The procedure works well and today problem (LB, TLB#50, accessible point) might be a rather easy done and what is more, the gel glue residue serves later as a sealing agent.

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Garage leaks

The reason of the garage leaks is found: the fail of gaskets used as intermediate and sealing elements in the garages locks mechanism. Convention material of the gaskets (plain rubber) was weakened by prolonged (~6 years) affection of the liquid so, the driving pins of the locks punched the gaskets. The base of the problem is that current design create unnecessary excessive tension at the gaskets top.

Possible remedies:• Primary steps – just replace the failed item with the fresh ones – we sure know it might withstand more than 3-4 years of the operations• Change the material of the gaskets – to NBR or silicon rubber based one => Not enough for the complete insurance because it is essentially “mechanical” problem• Change the design: the locks driving pin sealing must be revised and corrected as well ar gaskets housing. Options under consideration:

• O-rings sealing of the driving pin• Membrane located closer to the piston and out of the driving pin location

All the measures related to the design change have to be taken after scrupulous studies and tests (under way)

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Garage leaks

The idea of garage drainage (leak collector) looks attractive but depends very much on the real garage surroundings with other equipment. Evidently it might be an individually designed container of some kind with draining pipe or absorbent to direct or absorb the liquid drops.

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Flexible pipes

Last year a set of pipe samples were affected to artificially ageing and found to be adequate to our task. Now we can do some exercises with the real things use as PP interconnections in the pit. They are the same and used with the same conditions as those one lying in the flexible chain.• A number of pipes removed from the pit supposed to be tested at a high pressure applied periodically (100-200, ~8 bars) • Half of them affected artificially ageing• All of them are tested once more by periodical pressure• Compare the conditions of both sets: if there are no difference, all of the pipes resting in the pit are safe for the next few years…

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Global measures

The installation of the new liquid storage unit (WS) drastically changes the mode of operation:

• The liquid now is inside the piping just for the scan period => decrease the pressure on the equipment (physical and chemical) by a factor of tens• Piping emptiness create a good opportunity for regular air pressure test for the whole impermeability so, a leak might be detected in advance• Regular inspection of the garages status should became a mandatory thing• We are going to decrease the salt concentration a little bit just to be on a safe side; that is possible now after the sources capsules latest examination

At the same time it is unwise not to provide for every eventuality – install additional protection for the sensitive equipment close to Cs one…

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Conclusions

• The current leaks might be eliminated at some cost and the system sure be safe the next 2-3 years.• During the next year the design of the garage locks driving mechanism has to be revised, all the garages upgraded